Slurries or liquid-solid mixtures in which solids are dispersed in water or other carrier liquids, at some stage of processing ordinarily require at least partial separation of the solids from the liquid carrier for either removing contained solids or recovering them for an intended use, usually after further processing. Aside from the Fourdriner screens peculiar to paper making, numerous types of separating devices have been used for deliquefying such slurries, including filter or other presses, centrifugal separators and various forms of screens.
For separating fibrous and other solids from slurries in which the solids are floating or suspended in the carrier liquid, whether purposed for pollution control or to recover usable solids, such as natural or synthetic fibers, a current practice is to flow the slurry over a screen having a flow surface formed by laterally spaced screen wires or bars disposed perpendicular to the flow direction of the slurry. Whether curved or horizontal or inclined flat screens and stationary or vibrating, a problem posed in separating solids by screens from a flowing slurry, particularly when the solids are or include fibrous materials, is the tendency of the fibers to clog or blind the screen openings between the screen wires. Proposed solutions for this problem are those of Ginaven U.S. Pat. No. 3,451,555 in which the screen wires have concave top surfaces for producing an undulating motion in the flowing slurry and Fontein U.S. Pat. No. 2,942,730 in which flat-topped and sided screen wires each receives slurry on a transition surface leading upwardly to its flat top from a line of intersection with its leading side. Another proposed solution is that of Ginaven U.S. Pat. No. 3,777,893 in which the screen wires are bowed and thinned between the longitudinally extending widely spaced tie rods by which they are interconnected to cause the slurry to move away from the tie rods and concentrate along the troughs of the screen wires. It is to an improvement in self-cleaning screens for separating fibrous and other solids from flowing slurries that the present invention is particularly directed.